Drop in Concentration as reaction progresses

[jaz1409]

Homework Statement

I am currently doing an investigation into the reaction between different acids and magnesium metal. I want to try and show that by using a large volume of acid the concentration drop as the reaction progresses is significantly reduced. Is there any way of doing this?

Homework Equations

Mg (s) + 2 HCl (aq) --> H2 (g) + MgCl2 (aq)
Mg (s) + 2 H+ (aq) --> H2 (g) + Mg+2 (aq)

The Attempt at a Solution

Well I thought that by working out the moles of H+ ions present at the beginning of the reaction and at the end of the reaction may help. Other than that, I would just like to be pointed in the right direction.

 

[chemisttree]

You could remove an aliquot of solution at several intervals and titrate the acid. Plot the concentration of acid vs time for your result.

The results might surprise you, though...

 

[jaz1409]

well, so far I have found out the number of moles of HCL in 100cm3 of acid and then found the number of moles of H+ ions. I then found the percentage drop.

 

[chemisttree]

What did you notice about the reaction rate?

 

[jaz1409]

well, I worked out that the maximum drop in concentration theoretically was 5.20% which for a concentration of 0.8 M is not significant.

 

[chemisttree]

Thats what I thought would happen. Also, the metal surface area is shrinking during the reaction. This will cause the greatest change in rate of reaction.